Field
Exemplary embodiments relate to a light emitting diode (LED) driving circuit and an LED lighting device, and more particularly, to an LED driving circuit and an LED lighting device that may control a color temperature using a dimmer.
Discussion of the Background
Generally, a diode device for light emission such as a light emitting diode (LED) has been driven only by direct current (DC) power due to its diode characteristics. Therefore, a conventional light emitting apparatus using an LED has been restrictively used in that a separate circuit, such as a switching mode power supply (SMPS), is generally included in the light emitting apparatus in order to be driven by alternating current (AC) power of 220V that is currently used at home. As such, a circuit of the light emitting apparatus may become more complicated, and costs for manufacturing the light emitting apparatus may be increased.
In order to solve these problems, research of an LED that may be driven even by AC power has been conducted, for example, by connecting a plurality of light emitting cells in series with or in parallel to each other.
In addition, a sequential driving scheme of LEDs using AC power has been suggested. According to the sequential driving scheme, when a lighting device including three LED groups is applied with an increasing input voltage over time, a first LED group first starts to emit light at a first forward voltage level to a second forward voltage level higher than the first forward voltage level, a second LED group connected in series with the first LED group starts to emit light at the second forward voltage level to a third forward voltage level higher than the second forward voltage level, and a third LED group connected in series with the second LED group and the first LED group starts to emit light at the third forward voltage level to a fourth forward voltage level higher than the third forward voltage level.
When the lighting device is applied with a decreasing input voltage over time, the third LED group first stops emitting light at the second forward voltage level to the third forward voltage level, the second LED group stops emitting light at the first forward voltage level to the second forward voltage level, and the first LED group finally stops emitting light at a voltage is level equal to or less than the first forward voltage level. In this manner, an LED driving current of the lighting device may be approximated to the input voltage.
Such LEDs, which may be driven sequentially using general AC power, may be driven regularly, but have limited characteristics, for example, implementing only a predefined color temperature depending on the characteristics of the LEDs.